In Blood Banks, for instance in Hospitals, many blood specimens are stored in test tubes for indefinite periods in refrigerators or freezers.
In a large Blood Bank there may be hundreds or thousands of different specimens in storage. The test tubes are set in racks and the racks are stacked in a refrigerator or freezer. The test tubes and racks are generally labeled with pieces of tape with writing thereon.
If it is desired to retrieve a particular specimen it is very difficult to get the proper rack and test tube because it is difficult to read the labels and the tapes frequently fall off. This can lead to serious consequences.